Correspondence—Mr. G. H. Kinahan. 285 
limit of glaciation in the countries, and this would show that some 
equalizing effect was produced by the diminished and _ partial 
diverted Gulf-stream, as Dr. Croll’s theory requires. 
Having recently been subjecting the whole of the evidence on 
the subject of “ geological climates ” to a careful examination, I may 
state, that I have arrived at an important modification of Dr. Croll’s 
theory, which will, I believe, obviate the chief objections that have 
hitherto been made to it. The subject will be fully discussed in a 
volume I am now engaged in printing. 
Croyvon, April 18th, 1880. AuFrrep R. WALLACE. 
PERMIAN ROCKS. 
Sir,—The investigation at present occupying the attention of 
Messrs. Teall and Wilson is, I believe, one connected with a most 
important geological question,—a question that hereafter must 
engage more attention than it does at present. These inquirers 
however are in advance of their age, and have much up-hill work 
before them. Nevertheless I suspect that hereafter geologists will 
have to allow that the rocks of the so-called “‘ Permian Formation,” 
are only ‘passage-beds” between Carboniferous and _ Triassic 
formations,—palzontologically allied to the first, but stratigraphically 
to the second. Before this is accomplished, a great deal of work will 
have to be done in collecting and arranging in tabular form all the 
evidence in connexion with the rocks of this so-called formation ; 
and thus prove the hiatus said to exist in different places to 
be imaginary. 
In Ireland there are only small exposures of Permian rocks, yet 
they appear to be very important, as they point to the true character 
of the rocks that have been elevated into a ‘‘ formation.” They are 
as follows :— 
Permians of Armagh.—These rocks are in the vicinity of Armagh 
town, and apparently are the conglomeratic basal beds of the Trias. 
There is no evidence to prove an unconformability between them and 
the Trias. 
Permians of Benburb.—These are exposed in the Blawater valley 
on the nearing of the counties Tyrone and Armagh. They un- 
doubtedly belong to the Carboniferous, as they lie conformably on 
a true Carboniferous limestone, while in the centre of the group is a 
bed carrying typical Carboniferous fossils. 
Permians of the Lagan Valley.—Those near Moira are of a some- 
what similar type to those of Armagh, and here, as there, seem to be 
at the base of the Trias; while those at Cultra would have been 
classed with the associated Triassic beds but that they carry fossils 
similar to those of the Durham Permians. 
Tullyconnell Permians.—These rocks, although apparently belong- 
ing to the Trias, carry fossils similar to those in the Cultra beds. In 
one locality (Templereagh) they are very instructive; here, while 
sinking a coal-pit, a dolomite 16 feet thick was found, strati- 
graphically belonging to the Trias, but paleeontologically to the 
Permian. The Permians of Tullyconnell and Cultra, although 
